The objectives of this proposal are to continue the prospective, phase III, randomized study of polycythemia vera, to conduct efficacy trials of new agents for the treatment of polycythemia, and to continue the myeloproliferative disease study. By means of protocols under study the optimum therapy amongst phlebotomy, radioactive phosphorus and chlorambucil resulting in the least morbidity and the longest survival will be selected, the natural history of polycythemia vera will be characterized and the modifying effects of myeolosuppressive therapy determined. Cytogenetic abnormalities are being detected by studies of bone marrow and histopathologic marrow examinations are being performed. The myeloproliferative diseases study is an extension of the existing study of polycythemia vera. The purposes are to: 1) characterize and reclassify the diagnostic criteria for these disorders in terms of clinical manifestations, morphologic abnormalities (blood and bone marrow), cytogenetics, blood chemistries, tests of hematopoietic function; 2) observe previously untreated patients throughout their disease with respect to the rate of disease progression and survival, incidence of acute leukemia and other major complications and to describe prognostic correlations; 3) to determine the best available form of treatment (drug, splenectomy and radiation) specifically designed according to the major clinical manifestations.